Strip mill control



FIG. I.

Oct. 24, 1944. J. L. wHlTTEN 2,360,995

STRIP MILL CONTROL Originazl Filed Jan. 18, 1939 6 Sheets-Sheet l ILEmvENroR JAMES LwHITTEN Oct. 24, 1944. J. l.. WHITTEN STRIP MILL CONTROLOriginal Filed Jan. 18, 1939 6 Sheets-Sheet 2 SII SID INVENTOR JAMES l..WITTEN A TToRN Oct. 24, 1944. J. L. wHlTTEN 2,360,995

STRIP MILL CONTROL Original Filed Jan. 18, 1939 6 Sheets-Sheet 3 FIGA.

llllllllllllH Hllllll llll l-lllllllll I INVEN TOR.

JAMES L.. WHITTEH A TTORN Oct 24, 1944 J. l.. wHlTTEN STRIP MILL CONTROLOriginal Filed Jan. 18, 1959 6A Sheets-Sheet 4 Om mm Nm INVENTOR JAMESL. WHITTEN A ORNEY Oct. 24, 1944. J. wHlTTEN 2,360,995

STRIP MILL CONTROL Original Filed Jan. 18, 1939 6 Sheets-Sheet 5 s[11:12: |11 mul |1- [HHH IN1/wrox JAMES L. wHlTTEN f l l/ I Oct. 24,1944. .1. l.. wHlTTEN 2,360,995

` STRIP MILL CONTROL Original Filed Jan. 18, 1939 6 Sheets-Sheet 6 IN VEN TOR.

JAMES L. WHITTEN Patented ocr. 24, 1944l STRIP MILL CONTROL James L.Whitten, Lakewood, Ohio, assignor to The Brown Instrument Company,Philadelphia, Pa.. a corporation of Pennsylvania Y Original applicationJanuary 18, 1939, Serial No. 251,557. Divided and this application April16, 1943, Serial No. 483,233

8 Claims.

The present invention relates to and comprises improvements in theapparatus for controlling the operation of a continuous strip oranalogous metal rolling mill, in which the work pieces, each initiallyin the form of a billet, ingot, or other compact body, are subjected torepeatedgrolling operations, effecting relativelygreat reductions in thecross section of the work pieces.

The general object of the invention is to pro.

vide apparatus for controlling the operation of a continuous metalrolling mill of the character The regulating operations effected inaccord-k ance with the present invention, ordinarily comprise variationsin the rate at which fuel supplied to the billet furnace in accordancewith the heat requirements of the mill and preferably an automaticproportioning of the'supplies of combustion air and fuel, and compriseroll adjustments which may comprise either or both adjustments of theroll speeds and adjustments of thedisplacement of cooperating rolls tovary the roll passes, whereby compensation may be obtained for theincrease in power required to operate the rolls, and for the tendency ofthe cooperating rolls tospring apart and increase the roll passthicknesses, as the temperature of the work pieces passing through themetal decreases.

While the temperature measurements can be eiected with variousinstrumentalities, I consider it practically desirable, if notessential,"to meas.-

.ure the temperature of the work pieces `at difresultant of the furnacecondition prevailing in the furnace for a considerable preceding periodof time.

A still more specific object of the present invention, therefore, is notonly to properly correlate the control eiects due to the differenttemperature measurements, but to eifect a control system compensation,whereby a change in a plant load condition or demand for heat may resultin a quick adjustment of the heat supply suillcient to check thetendency of the change in heat requirement to change temperatureconditions, but not large enough to prevent some temperature variationas a result of the change in load demand, coupled with a delayed furtheradjustment which will tend to restore the normal temperature conditions,without giving rise to including one form of the present invention;

Fig. 2 is a diagrammatic representation of two interlocked measuring andcontrol instruments including in the apparatus shown in Fig. 1;

ferent points along the path of work travel furnace temperaturemeasurement obtained must necessarily involve/a time lag factor, becausethe Fig. 3 is a diagrammatic representation of temperature measuringapparatus included in Fig. 1, and comprising a photoelectric celldirectly responsive to the work temperature moving in front of the cell;

Fig. 4 is a somewhat diagrammatic representation of one form of rolladjusting means;

Fig. 5 is. a somewhat diagrammatic representation of another rolladjustment mechanism;

Fig. 6 is a diagrammatic representation of a billet furnace andassociated furnace control provisions which may be regarded as a moredetailed and specific illustration of apparatus generically illustratedin Fig. 1;

Fig. 7 is a diagrammatic representation of control means of theproportioning system type, which may be used alternately with controlprovisions shown in Fig. l;

Fig. 8 is a diagrammatic representation of a modification of a portionof the apparatus shown in Fig. 1;

substantial heat capacity of the furnace and the vbillets thereinmeansthat the furnace temperature at anyinstant isl necessarily an average orFig. 9 is vafdiagramrnatic representationof a second modification lof aportion of thecontrol system shown in Fig. 1; and

` Fig. 10 isl a diagrammatic illustration of 'still Vanothermodification ofthe apparatus shown in Fig. 1.

, I'he embodiment of the inventionillustrated Y diagrammatically in Fig.1 comprises a plurality, three being shown, of heating furnaces A whichsupply billets to the conveyor system B of a continuous strip metalmill. The latter, as shown, comprises a scale breaker C through which-the billets received from the furnaces A are passed to roughing rolls,shown as comprising four stands D', D2, D3 and D4, arranged in series.

' From the roughing rolls, the billets are passed on to a holding tableE, from which they pass to the finishing rolls, shown as comprising sixstands, F', F2, F3, F4, 1is and F, arranged in series.

As dlagrammatically shown in Fig. 1, each furnace is supplied with fluidfuel through an individual branch G2, at a rate controlled by acorresponding control instrument G, and associated regulator G'. Eachinstrument G of Fig. 1, as hereinafter explained, is of a known type,adapted to adjust the corresponding regulator G', in joint response to atemperature condition of the corresponding furnace A, which is measuredby the instrument G, and to the temperature of the billets as they passfrom the scale breaker C to the roughing rolls. The last mentionedtemperature is measured by an instrument I, which, upon a variation insaid temperature, effects a corresponding adjustment of each of thethree instruments G. As shown, the temperature condition measured byeach instrument G, is that to which a thermocouple H in the roof loi.the` corresponding furnace, responds.

control of an instrument J -responsive to said temperature. Theadjustment may compensate for a variation in billet temperature eitherby varying the distance between the two rolls of each stand, or byvarying the roll speed. The third and fourth stands of roughing rolls D3and D4, are similarly adjusted Vin accordance with variations in thetemperature of the billets passing on to the holding table E, by aninstrument K responsive to that temperature. The different stands offinishing rolls F' and F6, are subject to simultaneous adjustment by aninstrument L, responsive to the temperature of the rolled billets orstrips, leaving the finishing rolls.

Each of the various instruments G, I, J, K and L may be of any usual orsuitable type adapted to serve the required control purposes. As shown,the instruments are all of the commercial type known as the Brownpotentiometer, but the instrument I is of a form which effects controloperations by modifying electric circuit connections, while each of theother instruments includes so-called air controller provisions, foreffecting control actions by varying a control air pressure.

The characteristic features of the instruments of both forms, in so faras they need to be referred to herein, are shown in Fig. 2, which is adiagrammatic illustration of parts of the instruments G and I. As shown,the instrument G includes a pen carriage M in threaded engagement. witha shaft N, which, by its rotation in one direction or the other, adjuststhe pen carriage longitudinally of the shaft. The shaft N is rotated inresponse to variations in the quantity measured by the instrument,through power means, which, as diagrammatically shown in Fig. 2,comprises a reversible electric motor O having its armature shaftconnected to the shaft N, The

instrument G also includes a spirally grooved shaft NA, parallel to theshaft N, and in threaded engagement with a control table P, whichcooperates for control purposes with the pen carriage M of theinstrument, as hereinafter described. The shaft NA, as diagrammaticallyshown in Fig. 2, is rotated by a reversible electric motor OA when thelatter is energized as hereinafter described. The instrument I shown inFig. 2, is exactly like the instrument G in so far as above described,but its motors corresponding to the above mentioned motors O and OA, aredesignated OC and OB, respectively.

Associated with the motor O of each instrument G, are circuit provisionsthrough which that motor is energized for operation in one direction orthe other by an increase or decrease, respectively, in the temperatureof the corresponding furnace thermocouple H. Those circuit provisions asshown in Fig. 2, 'comprises electric supply conductors I and 2, theconductor I being permanently connected to the common terminal of themotor O, which is energized for operation in one direction or the otherby the connection of one or the other of its other terminals 3 and 4, tothe supply conductor 2. As shown, the latter is connected by a conductor5 to the pointer Q of the instrument galvanometer Q. The latter has oneterminal connected by a conductor I to one terminal of the thermocoupleH, land has its other terminal connected by a conductor 1 to one end ofa potentiometer resistance 9. The second terminal of the thermocouple His connected by a conductor ll to a slider or contact arm 8,diagrammatically shown as adapted to be oscillated by the rotation ofthe shaft N, and in engagement with a potentiometer slide Wire resistor9. 'I'he latteris energized by a battery or other source of current IIJ.

'Ihe pen carriage M and control table P of eachinstrument G cooperate toproduce control effects, by effecting angular adjustment of the appervalve of an air controller element included in the instrument, throughconnections of the character disclosed and claimed in the Moore PatentNo. 2,093,119 granted September 14, 1937.

Those connections comprise a cam P', hinge connected to the controltable P, and given oscillatory movements by the movement in thedirection of the shaft N, of a cam engaging part M carried by the pencarriage M, when the latter is in the control range, in which the part Mengages the inclined edge 1020 of the cam part P. The part P is insliding engagement with a barlike part P2 which shares the oscillatorymovements of the cam `P', andthereby, through mechanical connectingparts including a link P2. a rock ng element P4, and a link P5, givesoscillatory movements, to the flapper valve actuating element S of theair controller.

The air controller shown is of a form fully disclosed in the patent ofColeman B. Moore, No. 2,125,081 granted July 22, 1938, and now inextensive commercial use. The actuating member S is a lever pivoted atS' to an adjustable fulcrum member S2, in the form of a lever having astationary fulcrum pivot S3. The movements of the lever S move a flappervalve S4 away from. or permit it to approach a nozzle or bleed orificemember S5. The apper valve S4 is mounted on a stationary pivot, and isbiased for movement in the direction in which it approaches andrestricts the discharge through the nozzle S5. The

lever S acts on the flapper through a pin S carried by a depending armof the lever.

The nozzle S.receives air from a pipe S'I supplying air at a suitableand approximately constant pressure, through a restricted passage formedby a small bore pipe S8, included in a pilot or booster valve mechanismS9, so that the pressure in nozzle S which constitutes the primarycontrol pressure of the control apparatus, increases and decreases asthe iiapper valve S4 moves toward and away from the nozzle. primarycontrol pressure is transmitted by a pipe 81 to a chamber S11 o1' thepilot valve mechanlsm. One wall of that chamber is movable, andseparates the chamber S11 from a second pilot valve chamber S12. 'Ihepressure in the latter is regulated by a valve means S13 actuated by thesaid movable wall. 'Ihe pressure in the chamber S12 is thus maintainedin constant proportion to the primary control pressure in the chamberS11` and constitutes the ultimate control pressure of the apparatus.

The said ultimate control pressure is transmitted by a pipe S14 to thepressure motor chamber of the corresponding valve G', and to mechanism,T, forming a part of the control apparatus, and adapted. following andas a result of each initial change in the ultimate control pressure,effected through link P5. to give the lever S2 an initial follow-upadjustment, and a delayed compensating adjustment. The follow-unadjustment neutralizes a portion of the initial adjustment of theflapper valve S4. The delayed compensating adiustment slowly neutralizesmore or less of the effect cf the preceding follow-up adjustment.

The mechanism T comprises bellows elements` two of which are connectedby a connecting rod T', which carries a projection T2. The latter actson lever S2 through a lever T3 pivoted at T4, and a thrust pin T5interposed between the levers T2 and S2. The pin T5 is supported by amember 'I6 adjustable to vary the leverage with which the lever T3 actson the lever S2. The latter is biased for movement in the clockwisedirection, as seen in Fig. 2. Changes in the ultimate control pressureactuate the mechanism T to give longitudinal movements to the rod T' byvirtue of the fact that the ends of the latter are connected to themovable ends of oppositely facing bellows elements, each of which issurrounded by a second bellows element having a movable end, and isexternally subjected to the pressure in the corresponding interbellowsspace T1 or T8.

The ultimate control pressure acts externally on the bellows elementenclosing the space T". The spaces T1 and IB are lled with liouid andare in communication through a conduit T9, ow through which is variablyrestricted by the adjustment of a valve T10.

Further reference to the details of construction of the instrument G andthe air pressure mechanism included therein are unnecessary, becausesuch instruments and mechanism are not only fully disclosed in the abovementioned Moore patents, but are in extensive commercial use. Moreover,those details form no part of the present invention, which may bepracticed with control instruments differing in form and type from thosedisclosed herein, though it is to The4 be noted that for the attainmentof certain advantages of the present invention, the control instrumentsshould include provisions for modlfying initial control adjustments bysubsequent follow-up or follow-up and compensating ad- Justments.

On the assumption that the pen carriage M of the instrument G moves tothe right or left in response to an increase or decrease in the con trolrange, a movement o! the pen carriage to the left as a result of adecrease in the temperature of the thermocouple H, results in acounterclockwise adjustment of the lever S about its pivot S',permitting the dapper valve SA1 to approachthe nozzle S and therebyincrease the primary control pressure. The resultant increase in theultimate control pressure gives the valve G' an opening adjustment, andwhen transmitted to the mechanism T, increases the pressure on thebellows element forming the outer wall of the space T7, contracting saidbellows element and thereby correspondingly contracting the smallerbellows element connected to the adjacent end of the rod T'. The extentof the movement thus given the rod T', depends upon the magnitude of thechange in the ultimate pressure, and on the natural resiliency of thebellows elements and other spring bias force opposing the movement ofthe rod T'.

The movement of the rod T to the left as a result of the increase in theultimate control pressure, acts through the pin T2, lever T3 and thrustpin T5 to give a counter-clockwise adjustment to the lever S2 about itspivot S3 and thereby move the dapper valve S4 away from the nozzle S5.This follow-up adjustment of the apper valve partially neutralizes theeiiect on the control pressures of the initial adjustment of the iiappervalve.

The increase in the ultimate control pressure, which, through its actionon the bellows forming the outer Wall of the space T7, gave the rod T'its above described movement to the left, also increased the pressure inthe space '11". When the pressure in T7 is thus increased, relative tothe pressure in the other interbellows space T8, liquid begins to flowinto the last mentioned space from the space T'I through the restrictedconduit T9. As the pressure in the two interbellows space equalizes, therod T moves slowly to the right under the action of the resilient forcestending to restore normal lengths of the small bellows elementsconnected to the ends of the rod T'. This second delayed movement to theright of the rod T', gives a compensating adjustment to the flappervalve S4 tending to neutralize the .previous and more rapidly effectedfollow-up adjustment, and thereby to increase the control pressures.

As diagrammatically illustrated, the instrument I, through itselectrical control provisions, controls the energization of the motor OAof the instrument G, shown in Fig. 2, and thereby controls the positionof the cam P longitudinally of the shaft NA. Such adjustment of thecontrol table P and its cam P is commonly referredto as a control pointadjustment, and varies the furnace temperature which the instrument Gtends to maintain.

The motor OB may be operated to adjust the pen carriage M of theinstrument I in accordance with changes in the temperature of thebillets leaving the scale breaker C, through temperature measuringprovisions associated with the instrument, of any known or suitabletype,

one known arrangement being illustrated diagrammatically in Fig. 3 andhereinafter described. As shown in Fig. 2, the adjustment of the controltable P of the instrument I is sublect to manual control.

erable switch member 643.

The relative adjustments of the pen carriage bi and control table P ofthe instrument l', control. the energization of the motor OA oi theinstrument G shown in Fig. 2, through a switch lever R pivoted at it onthe table P oi instrument i, and carrying a cam roll R2 at its free end,which is adapted to engage the inclined portion of a cam member 'M2carried by the pen carriage M of the instrument i. n a decrease in thebillet temperature measured by the instrument l, and correspondingadjustment to the lert oi the pen carriage M of that instrument, theswitch lever R is tilted clockwise, whereupon the switch contact R3carried by said lever, and connected tothe supply conductor 2, engages acontact connected by a conductor i5 to one terminal or the motor Ofi ofthe instrument G. The common terminal oi that motor is permanentlyconnected by a conductor it to the supply conductor i, and said motor 0Ais then energized to adjust the pen carriage P of the instrument G tothe left as seen in lilg. 2.

The last mentioned adjustment produces a control effect on thecorresponding regulator G in the same direction as is produced by adecrease in the temperature measured by the corresponding instrument G.Conversely, an increase in the billet temperature measured by theinstrument l results in a counter-clockwise'adjustment of the switchlever R, whereby its Contact 'R3 is adjusted to connect the supplyconductor 2 to a conductor il, running to the third terminal of themotor OA of the instrument G. The resultant energization of the lastmentioned motor adlusts the control table P oi the instrument G shown inFig. 2 to the left, and thereby produces the same modification of thecontrol action of the instrumentl G as would be produced by an increasein the furnace temperature 'therrnocouple l-i connected to thatinstrument. Since all the instruments G are subject to similarsimultaneous adjustments by the instrument l, an increase or decrease inthe temperature at `which the billets leave the scale breaker C, resultsin a corresponding decrease or increase respectively, in the rate offuel supply to each of the furnaces A.

'in Fig. 3, l have illustrated an arrangement in which the instrument Iis combined in a, known manner with photoelectric cells, thermionic tubeamplifying means, and current regulating means. As shown in Fig. 3,light is radiated by the billets leaving the scale breaker to aphotoelectric cell U, which is thus made responsive to the billettemperature. The cell U' is connected in series with a secondphotoelectric cell UA, receiving light from a lamp ua, and with twosimilar sources oi direct current it and l@ diagrarnmatically shown asbatteries, As shown, one terminal oi the cell U is connected by aconductor 2li to the negative side of the battery it, and the secondterminal of the cell ua is connected by a conductor 2i of one terminaloi the cell U, which has its other terminal connected by a conductor 22to the positive side of the battery it. The positive side of the batteryiii is connected to the negative side of the battery i@ by a conductorThe intensity of the light from the lamp ua is regulable, and isnormally so adjusted that the two similar photoelectric cells U and UAare similarly illuminated, and since the two current sources i8 and i9are similar, the circuit including those sources and the photoelectriccells is then in balance, in the sense that there is substantially nodiierence in potential between the conductors 2l and 23. This balance isdisturbed by an increase or decrease in the billet temperature, andconsequent change in the intensity of the light transmitted to the cellU. The difierence in potential between the conductors 2i and 23 thencreated is amplied by means including a thermionic tube 2d, which hasits control grid connected to the conductor 2i and has its plateconnected to the positive terminal of a battery 25 which has itsnegative terminal connected to the conductor 22. A conductor 265connected to the conductor 23, and a conductor il connected to thecathode of the tube 2d, constitute the output terminals of theamplifying unit including the tube iid, the terminals 26 and 2li beingconnected by a suitable high resistance 2t.

The amplied potential difference between the conductors di and it,resulting from a variation in billet temperature, is transmitted by theterminals 2b and ill to a device W, in which said difference may befurther amplified, and through which current is supplied to the terminalconductors il@ and i3d oi the lamp ua, at a rate which is increased ordecreased as a result of said potential difference, as required to againmalte the illumination ci the cells U and UA equal, and therebyrebalance the circuit including the cells U and 'UA and current sourcesit and ld. The instrument l is arranged to measure and record theenergizing current of the lamp ua, and thereby provide a billettemperature measurement record. To this end, in the form shown, thepotentiometer slide wire resistor 3l of the instrument I is energized bythe device W through conductors 35 and and the potentiometer slide wirecontact carried by the pen carriage M of the instrument I and engagingthe resistor 3l', which, as diagrarmnatically shown in Fig. 3, extendsalongside of the path oi movement of the pen carriage, is connected by aconductor1 38 to the device W.

The device W need not be illustrated or further described herein as itsparticular construction forms no part of the present invention, but onthe contrary may well be of the type disclosed in the Nichols Patent2,187,613, of January i6, i940, and of a particular form of said type,which is now in commercial use, and is Harrison Patent 2,245,033, ciJune l0, 1941. In said commercial form of apparatus, the motor OB of theinstrument "i is of the alternating current type, comprising twowindings, one of which has its terminals 35 and dil connected to thesupply conductors ll and 2, while the second motor Winding has itsterminals 3b and 39 connected to the device W, which serves to impress apotential diierence on those conductors oi a phase which leads or lagsbehind the potential of the supply conductors l and 2, about as thebillet temperature varies in one direction or the other from thetemperature corresponding to the existing illumination of the lamp ua.The phase of the current supplied to the motor by the conductors 3T and38 on an increase in the billet temperature causes the motor OB tooperate in the direction to increase the intensity ofl the light emittedby the lamp ua until balance is then established accordingly.Conversely, when the billet temperature drops, the phase relation of thecurrent supplied to the two motor windings becomes such that the motorOB operates in the direction to diminish the illuminating effect of thelamp ua until balance is reestablished. In the commercial form ofapparatus illustrated in the Harrison application, the same motor OBwhich adjusts the pen carriage of the temperature measuring of thepotentiometer measuring instrument, also adjusts means for regulatingthe current supply to a lamp corresponding to the lamp ua, and in Fig.3, OB diagrammatically represents an operating connection between themotor OB, and current regulating means included in the device W forregulating the intensity of the current supply to the lamp ua.

The instrument J in conjunction with an associated device W is adaptedto measure the temperature of the billets as they pass from the rollsD1l to the rolls D3, just as the instrument I and its associated deviceW measure the temperature ofthe billets leaving the scale breaker C. Theinstrument J, which controls the operation of the rst and second standsof roughing rolls D and D, may effect that control through electricalcontrol provisions, analogous to those through which the instrument Icontrols the adjustment of the control table P of the instrument G. Asshown, the instrument J may include pneumatic control provisions likethose included in the instrument G shown in Fig. 2. As shown, theultimate control pressure of the instrument J, which varies with thebillet temperature measured, is transmitted by a pipe J to a penumaticcontrol element J2 associated with each of the roll stands D and D2.

Aspreviously indicated, the effect of a variation in billet temperatureon the operation of the rolls through which the billet is passed may becompensated for, in general, either by varying the speed of the rolls orby adjusting the rolls in the -manner required to vary the distancebetween' the rolls or roll pass thickness.

Thus, as shown in Fig. 4, the control element J2 is employed to controlthe operation of an intermittently operable reversible motor J1, thearmature shaft J11 of which is connected by suitable gearing to thethreaded roll adjusting shaft J1 of the roll stand D. As the temperatureof the billet passing through the roll stand D decreases, the motor J isset into `operation in the direction tending rto diminish the roll passthickness, so as to thereby compensate for the tendency of therelatively cold billet to spring the rolls farther apart than when ahotter billet is being rolled. In the arrangement shown in F18. 5, thecontrol element J2 shown controls the speed of the motor J111 directlydriving the rolls The instruments K and L in association with .K

corresponding devices W, are adapted to measure the temperature of thework as it passes over the holding table E, and leaves the finalfinishing rolls F', respectively, and to maintain control pressuresproportional to the temperatures measured in their respective controlpipes J', as the instrument J measures the temperature of the billetleaving the scale breaker and establishes the corresponding controlpressure transmitted through its pipe J. The devices J2 associated withthe different roll stands D3, D4, F'-F6, may adjust the speed ofoperation of rolls in those stands, or the roll pass relation of therolls, in the manner in which the instrument J controls roll pass andspeed adjustments as shown in Figs. 4 and 5.

. In Fig. 6, I have illustrated a recuperative type of billet heatingfurnace, of conventional type, and'having associated measuring andcontrol provisions somewhat more complex and highly developed than thosesuggested by the generic illustration in Fig. 1. In the arrangementshown in Fig. 6, the instrument GA, which measures and records thetemperature of the thermocouple H, may be exactly like the instrument Gshown in Fig. 2, except that its control operations are effected throughan electric motor OD and electircal control provisions like thosethrough which the instrument I controls the motor OA of the instrument Gshown in Fig. 2. The motor OD controlled by the instrument GA,automatically adjusts a control damper OD in the branch G2 of the supplymain G3, -through which fuel gas is supplied to the main burner G5 ofthe furnace.

The latter receives preheated air through a branch W' of the conduit WAreceiving preheated air for combustion from the recuperator means shown.

The flow of air through the branch W' to the burner G1 is controlled bya damper W2 adjustable to regulate the ratio of air to fuel supplied tothe burner G5. As shown, the damper W1 is automatically adjusted by adamper positioner 40, subject to the joint control of devices 4| and d2.The device 4I' is responsive to the differential of the pressures atopposite sides of a measuring orifice 43 in the branch W', and thedevice 42 is responsive to the pressure differential at opposite sidesof a measuring orifice 43 in the fuel supply branch G2. The instrument50, is shown as ar` ranged to measure and record the fuel gas flow4through the branch G2, and an indicating lnstrument 5l has indicatingpointers 52 and 53 adapted to indicate the rates at which combustion airand fuel gas are respectively supplied to the burner G5.

The furnace A' in the form shown in Fig. 6 `is provided with lower andupper auxiliary burners G7, receiving air for combustion from branchesW30A and W3, z respectively, of the recuperator outlet pipe WA, andreceiving fuel gas through individual branches Ga from the gas main G3.As shown, the rates at which fuel gas and combustion Vair pass to eachauxiliary burner G", is measured by means of corresponding measuringorifices 43 and instruments 5D and 5|, as are the rates of fuel and airsupply to the burner G5. The rates at which fuel gas and combustion airare supplied to each auxiliary burner (3'I may be automaticallycontrolled, as are the gas and air supplies to the main burner G5, but,as shown, the supply of fuel gas, and of combustion air, to eachauxiliary burnerl is regulated by a corresponding manually adjustabledamper 55.

The mechanism for automatically adjusting the damper W2 as required tomaintain the rates at which air and fuel gas are supplied to the burnerG5 in constant ratio, need not be further illustrated or described, asair and gas proportionlng arrangements suitable for the purpose are wellknown. In Fig. 6, an instrument 60, which may be exactly like theinstrument G in its measuring and recording features, is employed tomeasure and record the temperature of a thermocouple 6l in the chamberof the furnace A. The instrument 62 shown in Fig. 6 diiers from theinstrument 60, in that it includes a switch mechanism of well knownform, for connecting iive thermocouples 63, one at a time in regularsuccession to the meter. One of the thermocouples 63 is responsive tothe temperature in the pre,- heated air supply duct W. Two respond tothe respective temperatures in the heating gas inlets of the tworecuperators and two respond to the respective temperatures in theheating gas outlets of the two recuperators.

The temperature in the conduit WA is desirably maintained constant, andsomewhat lower than the temperature to which air is preheated in therecuperator. To this end, atmospheric air is drawn into the conduit WAthrough a port 64 in its wall at a rate, regulated, as shown, by adamper 65'adjusted by a damper regulator 66. The latter is controlled byan instrument GB which measures the temperature of a thermocouple 61responsive to the temperature, of the mixture of air supplied by therecuperators and air passing through port 64. The instrument GB mayadjust the regulator 66 through electrical control provisions, likethose through which the instrument I adjusts the motor OA of Fig. 2, orthrough pneumatic control provisions, like those through which eachregulator G of Fig. 2 is adjusted by the corresponding instrument G.

As will be apparent to those skilled in the art, my improved controlapparatus may take other forms and may be used for other purposes thanthose hereinbefore described. For example, as illustrateddiagrammatically in Fig. 7, an instrument GC, corresponding generally toone of the instruments G of Fig. 1 and similarly measuring a furnacetemperature, may give corrective adjustments to a corresponding fuelsupply valve through an electric motor and associated control provisionsincluded in a so-called proportioning system, which comprises means verydiii'erent in form from those shown in Fig. 2 for effecting compensatingadjustments analogous to those resulting from the iiow of fluid throughthe restricted passage T9 of Fig. 2.

The furnace temperature measuring instrument GC of Fig. 7, may beexactly like the instrument G of Fig. 2, in respect to its associationwith the thermocouple H, and with a second meter employed to angularlyadjust its control setting point shaft NA. carriage M of instrument GC,oscillates a lever RA pivoted on the control table P of the instrumentGC, and having a roller at one end in engagement with an edge cam M2carried by the pen carriage M. The oscillatory movements of the lever RAof Fig. 7 result through a connection RA', in corresponding movements ofa con tact 10 longitudinally of a slide wire resistance 1I, and throughla connection RA, in corresponding movements of a contact in thelongitudinal direction of two elongated contacts 93 and 94 arranged inend to end relation. The contacts 93 and 94 are spaced apart, so that ina neutral position voi? the contact' 15, the latter is between and doesnot engage either of the contacts 93 and 94.- The contact 15 is adapted,

-however,to engage one or the other of the contacts 93 and 94, when thecontact 15 is moved The movement of the pen y from its neutral positiondownwardly or upwardly, respectively, as seen in Fig. 7. The resistor1.1 is interposed between adjustable resistances 12 and 13, connected inseries with the resistance 1l between the proportioning bridge circuitconductors 14A and 15A, on which the bridge energizing potentialdifference is impressed, as shown, by connecting the conductors 14A and15A to supply conductors 2 and I, respectively. Said conductors 14A and15A are also connected by a slide wire resistance 16, and by twosolenoid coils 11 and 18 connected in series with one another. Thejunction point between the series connected coils 11 and 18 is connectedby a conductor 1.9 to the previously mentioned contact 10, and isconnected by a conductor to a contact 8| engaging and adjustable alongthe length of the slide wire resistance 16.

In a normal balanced condition of the apparatus with each of thecontacts 10, 15 and 8l in mid position, there will be no current flowingin conductor 19 or 80. When the Contact 10 is displaced from its midposition, thereby varying its potential relation With the supplyconductors l and 2, current will ow through the conductor 19, suchcurrent ow will make the current flows in the coil 11 and 18 unequal,and an armature 82 in inductive relation with the coils 11 and 18, willthereby be moved up or down, as seen in Fig. 1, accordingly as thecurrent llow in the coil 11 is then greater or less than the current owin the coil 18.

An up or down movement of the armature 82 moves a switch contact 83 intoengagement with contact 84 or contact 85, respectively. Contacts 84 and85 are connected to the terminals of the two iield windings 86 and 81,respectively, of a reversible relay motor 88. The contact 83 isconnected to the supply conductor I, and the second terminals of the4field windings of the motor 88 are both connected to the supplyconductor 2. The rotation of the armature of the motor 88 ad- .illsts afuel control valve G20 in the corresponding fuel supply pipe G2, andgives a follow-up adjustment to the contact 8l through operatingconnection 88' and 88", respectively.

In the operation of the apparatus shown in Fig. 7. on an increase, forexample, in the temperature of the thermocouple H, the resultantmovement of the pen carriage M to the right, gives a. counter-clockwiseadjustment to the lever RA. and an up adjustment to each of the contacts10 and 15. The up adjustment of the contact 10 diminishes the current owthrough the winding 11 and increases the current i'low through thewinding 18, with the result that the armature 82 moves downward,bringing the contact 83 into engagement with the contact 85. Thisenergizes the winding 81 of the motor 88, and the latter then rotates inthe direction to give a closing adjustment to the valve G20, and to movethe contact 8l downward as seen in Fig. 7. The down adjustment of thecontact 8 I, diminishes the current ow in the relay Winding 18, relativeto the current ilow in the relay winding 11, and continues until thecurrent flows through the coils 11 and 18 are again equalized.

If the control circuit of Fig. 7 including nothing beyond what hasalready been described, it could be proportioned and calibrated, to givestable regulation of the dropping characteristic type, whereby when thefurnace demand for heat, or load, increased above or fell below acertain intermediate normal furnace demand or load determined by theadjustment" of the apparatus, the resultant change in the rate of fuelsupply to the furnace, will be somewhat less than is necessary tomaintain the thermocouple H at the temperature which it will have withsaid intermediate normal demand for heat. In other words, with suchregulation the furnace temperature furnace maintained is not constant,but increases and decreases asl the demand for heat, or furnace load,respectively, decreases and increases.

To secure stable regulation While maintaining the temperature of thethermocouple H approximately constant, nothwithstanding fluctuations inthe demand on the furnace for heat, I employ suitable compensatingprovisions. The latter, as shown in Fig. '1, comprises a reversibleelectric motor 90 having two windings 9| and 92, each having oneterminal connected to the supply conductor 2. 'Ihe other terminals ofthe windings 9| and 92 are connected to elongated contacts 93 and 94,respectively, arranged in end to end alignment at opposite sides of theneutral position of the contact 15. The latter is connected by aconductor 95 to the supply conductor I. ln consequence, on an increasein the temperature of the thermocouple H and consequent movement to theright of the pen carriage of the instrument GC, and consequent upmovement of the contact into engagement with the contact 94, the motor90 will be energized for operation in one direction. Conversely, on adecrease in the temperature of the thermocouple H and movement ofthe'contact 15 down into engagement with the contact 93, the motor 90 isenergized for operation in the opposite direction.

The rotation of the motor 9D adjusts a Contact 96 along the slide wireresistance 12 in one direction, through a connection 90", adjusts acontact 91 in the opposite direction along the slide Wire 13. Thecontacts 96 and 91 form parts of shunt connections for short circuitingportions of the resistances 12 and 13, respectively. The adjustment ofeach of the contacts 96 and 91 thus produced, is always in the directionto augment the change in the potential of the contact 10, resulting fromthe adjustment of the latter, causing the adjustment of the contacts 99and 91. Thus, when the initial adjustment of the contact 19 is upward asa result of a decrease in the temperature of the thermocouple H, so asto diminish the potential difference between the contacts 10 and thebridge side conductor 14, the resultant adjustment of the contact 12will be to the right, thereby diminishing the portion of the resistance12 in circuit. The adjustment of the contact 96 diminishing the portionof resistance 12 in circuit is attended by a corresponding adjustment ofthe contact 96 to the left, thereby increasing the amount of theresistance 13 in circuit. Generally speaking, the adjustments of thecontacts 98 and 91 will lag behind, and proceed at a considerably slowerrate than the adjustment of the contact 10, which gives rise to theadjustments of the contacts 96 and 91. The relative rates at which thedifferent adjustments will be effected in any case should depend` asthose skilled in the artv will understand, upon various factors andparticularly upon the rapidity with which the furnace temperaturechamber measured by the thermocouple 8 varies in response to a change inthe rate at which fuel is supplied to the furnace.

The general principles of thepresent invention can be used in controlsystem arrangements specifically quite different from that shown inFig. 1. Thus, for example, in the system shown in Fig. 8, the instrumentI which measures the temperature of the billets leaving the scalebreaker C, is interlocked with, and controls the setting pointadjustment of each of three meters IA, each generally like the meter I,and employed to measure the temperature of the billets, respectivelydelivered tothe conveyor rolls B from the three furnaces A. `Theinterlocking conductors I 5', I6' and I1' connect the meters I and IA ofFig. 8, as the interlocking conductors I5, I6 and I1 connect the metersI and G in the control system shown in Figs. 1 and 2. Each meter IA isinterlocked in turn with the meter G, which measures the temperature ofthe roof thermocouple H of the corresponding furnace H, and controls thefuel regulator G for that furnace. In Fig. 8, the set of interlockingconductors I5", I6" and |1" which connect each instrument IA and thecorresponding instrument G, serve the same purposes as the conductorsI5, IB and I1, connecting the interlocked meters I and G of Figs. 1and'2v. In consequence, the regulation of each regulator G' is jointlydependent on three factors, namely the temperature of the correspondingfurnace A, the temperature of the billets discharged from that furnace,and the temperature at which the billets leave the scale breaker C.Except in respect to the described arrangement features, the controlsystem shown in Fig. 8 may be like that shown in Fig. 1.

In the control system arrangement hereinbefore described, the fuelregulators G of the different furnaces of a continuous mill, aresimultaneously subjected to adjustments dependent on the temperature ofa billet leaving the scale breaker C. 'In Fig. 9, I havediagrammatically illustrated an arrangement including a selector switchmechanism for successively subjecting the different instruments lG eachto a control point adjustment in accordance with the billet temperaturethen beng measured by the instrument I. As diagrammatically shown inFig. 9, the .interlocking conductor I5 extending away from theinstrument I is connected to the revoluble switch arm of a selectorswitch mechanism comprising three cooperating stationary switch contactsIUI arranged in a series extending circularly about the axis ofrevolution of 'the contactor IUD, and respectively connected bycorresponding conductors I5' each to a terminal of the motor 0A of oneof the instruments G, al1 of which are permanently connected to theconductor I5 in the arrangement shown in Figs. 1 and 2. Similarly, inFig. 9, the conductor l1 yextending away from the instrument I isconnected to the revoluble switch arm |02 of the 'selective switchmechanism including a second set of stationary contacts |03 arranged inseries .extending circularly about the axis of rotation of the contactor|02 so as to be successively engaged by the latter when it is rotated.Each contactor |03 is connected by a corresponding conductor |1' to thatterminal of the corresponding instrument G which is connectedpermanently to the conductor I1 inthe arrangement shown in Figs. 1 and2.

The revoluble conductors |00 and |02 may be mounted on a common shaftand continuously rotated by a. motor, or manually, as in selectiveswitch mechanisms in common use-to connect av plurality of measuringcircuits successively to a common measuring instrument. As will beapparent whether the selector contactors |00 and |02 are revolvedautomatically or manually, their engagements with the different contactsII|| and |02, respectively, may be synchronized with reference to thedischarge of billets to the mill from the different furnaces A, so thateach meter G will be interlocked with and subject to an interlockingadjustment by the instrument I, while the latter is measuring thetemperature of a billet received by the mill from the particular furnaceA, having its fuel regulator G controlled by that instrument G.

In Fig. 10, I have illustrated another embodiment of my improved controlsystem, differing from that shown in Fig. 1 in a number of respects. InFig, 10, the instrument J for adjusting the operation of the firstroughing rolls D' and U, is responsive to the temperature of the billetspassing to those rolls instead of t the temperature of the billetsleaving those rolls. Similarly, the instrument K adjusts the finalroughing rolls D3 and D4 in response to the variations of thetemperatures of the billets passing from the rolls D2 to the rolls D3,and the instrument L adjusts the various finishing rolls F-F6 inresponse to the temperature of the billets passing to the iinishingrolls over the holding table E. In Fig. l0, instruments IA areinterlocked I as Fig. 8, with an instrument I, which, in Fig. 10,measures the temperature of the billets leaving the final stand F6 offinishing rolls. Each instrument IA of Fig. l0, measures the temperatureof the billets passing to the mill from a particular furnace, and isinterlocked with, and regulates the control point adjustment of theinstrument G controlling the fuel supply to that furnace, as in thearrangement shown in Fig. 8. This case is a division of my applicationSerial No. 251,557, filed January 18, 1939, now Patent 2,343,392, issuedMarch 7, 1944.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of embodiment of my inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatus disclosed Withoutdeparting from the spirit of my invention as set forth in the appendedclaims and that in some cases certain features of my invention may beused to advantage Without a corresponding use of other features.

Having now described my invention, what I f furnace and on thetemperature of the work pieces passing through an intermediate portionof' said pathway, and means for adjusting one or more of said stands ofrolls on and in accordance with variations in the temperature of thework pieces approaching each stand of rolls so adjusted.

2. In a metal rolling mill, the combination with a plurality of standsof rolls distributed along the path of travel of heated Work .pieces toact successively on said pieces, and means responsive to the temperatureof the work pieces at a point along said path adjacent one of saidstands of rolls, and adapted, on each variation in the temperature atsaid point, to adjust the operation of said one stand of rolls in adirection and to an extent dependent on the direction and extent of saidvariation in temperature.

3. In a metal rolling mill, the combination with a plurality of standsof rolls distributed along the path of travel of heated work pieces toact successively on said pieces, and means responsive to the temperatureof the work pieces at a point along said path adjacentone of said standsof rolls and adapted on variations in the temperature at said point tocorrespondingly adjust the speed of the rolls in said one stand ofrolls.

4. In a metal rolling mill, the combination with a plurality of standsof rolls distributed along the path of travel of heated work piecestoact successively on said pieces, and means responsive to the temperatureof the Work pieces at a point along saidpath and adjacent one of saidstands of rolls and adapted on a variation in one direction or the otherin the temperature at said point t0 correspondingly increase or decreasethe roll pass thickness of said one stand of rolls.

5. In a continuous strip mill, the combination with a plurality ofstands of rolls distributed along the path of travel of heated workpieces to act successively on said pieces, and means separatelyresponsive to the temperature of the Work lpieces at different pointsalong said path and adapted, on a variation in one direction or theother at each of said different points to effect an adjustment dependentin direction and extent on the direction and extent of said variation inthe operation of stands of rolls respectively adjacent the said point atwhich the temperature variation occurs.

6. In a continuous strip mill, the combination with a plurality ofstands of rolls distributed along the path of travel of heated Workpieces to act successively on said pieces, and means separatelyresponsive to the temperature of the Work pieces at different .pointsalong said path and adapted, on variations in the temperature at saiddifferent points to correspondingly adjust the speed of the rolls instands of rolls respectively adjacent the said points at which thetemperature variations occur.

7. In a continuous strip mill, the combination With a plurality ofheating furnaces, of means for passing work pieces heated in thedinerent furnaces along a path of travel, a plurality of stands of rollsdistributed along said path, and means responsive to the temperature ofeach work piece moving along said path and to a temperature in thefurnace from which the work piece passed to said path, for regulatingthe rate of heat suD- ply to said furnace, and means for adjusting oneor more of said stands of rolls on and in accordance with variations inthe temperature of the work pieces approaching each stand of rolls soadjusted.

8. In a continuous strip mill, the combination with furnace means forheating work pieces to be rolled, means for passing said work piecesfrom said furnaces means along a path oi' travel, a plurality of standsof rolls distributed along said path, and means responsive to thetemperature of the work pieces moving along said path for regulatingsaid heating means and for adjusting some of said stands of rolls inresponse to variations

